The present invention relates to glass forming and trimming, and is an improvement to the inventions disclosed in Giffen U.S. Pats. No. 3,193,367 and 3,582,454. The former patent was directed to the problems encountered in trimming a newly formed article from surrounding sheet glass before the glass became chilled. The sheet was maintained in a spaced relationship from a wall of the forming die, which served as one trimmer edge, so as to minimize the cooling effect of the die on the sheet glass. The sheet was sheared by a trimmer slidably cooperating with the trimmer edge of the die. The latter patent was directed to the trimming of a laminated sheet so as to force an outer stratum over a central stratum of the laminate during the trimming operation.
U.S. Pat. No. 4,261,706 to Blanding et al relates to the use of a pair of cooperable rollers to form a plurality of uniform particles from molten material. The particles are initially joined together by thin web or edge portions within a sheet form, which is subsequently flexed in various directions to separate the particles along the edge or web portions.
In the past, the trimming techniques utilized for sheet glass required rather precise tolerances between the mold trim edge and the trimming tool, since the glass was sheared as the trimming tool cooperably slid along the trim edge, as shown in FIG. 1 and the above identified Giffen patents. Thus, as shown in FIG. 1, the critical dimension d in the operation was the dimension of the clearance between the trim edge 12 of the mold 10 and the trimmer 14. The necessary tolerances between the trimmer and the mold trim edge can usually be maintained within acceptable limits when the product to be trimmed is round by thermal sizing the parts. However, when a non-round trim is required, matching the tooling at the forming temperatures is extremely difficult since thermal size changes are not uniform. That is, since the sliding fit between the trimmer 14 and the mold trim edge 12 must be achieved at forming temperatures, the operating temperatures and behavior of the materials as they heat up must be known in order to accomplish the desired operable sliding fit. However, if the operating temperature change or the material behavior has not been accurately predicted, the critical dimension d will not be maintained, and the trimming will not function correctly due to either a binding or a loose fit between the trimmer parts 12 and 14.
When the product to be trimmed is round, a poor fit represented by the sliding clearance between the trimmer and the mold edge is not necessarily a serious problem since the fit can be adjusted with reasonable changes in tooling temperatures. However, when the product is not round, the problem becomes more serious since the longer mold dimension of the product to be trimmed changes a greater amount than the shorter dimension, and since the change is not necessarily uniform, it may result in an unacceptable trimming of the glass sheet G.